"If NASA hadn't failed us we'd have cities on the moon."
Thousands of spectators are expected to descend on the airport of the small desert town of Mojave, where the flight is scheduled for takeoff at 0647 PDT (1447 BST). A jet plane called White Knight will carry rocket SpaceShipOne slung beneath it to a height of 14,330 metres (47,000 feet).
At about 0750 PDT (1550 BST), the jet will release SpaceShipOne. The rocket will fire its engine for about 90 seconds to shoot above 100 kilometres - the official start of space.
Real time updates here.